The present invention relates to the automated formation of containers from sheet material preformed (e.g., scored, slotted, folded and glued) as a knocked-down-flat (KDF) container precursor. In particular, the invention concerns an apparatus and associated method that allow for an extension of conventional KDF set-up methodology and equipment to the formation of non-rectangular containers, i.e., containers having one or more oblique wall panels.
Conventional KDF precursors have four wall panels and associated end flaps which form a finished box of rectangular shape. Such KDF precursors are typically purchased in bulk by product manufacturers and erected at the manufacturer's facility using a case erector and sealing machine (case packer). A conventional case packer takes the KDF precursors, one at a time, from a stack and places them on a conveyor. The conveyor delivers the KDF precursor to a station where a gripper arm or the like is used to open the precursor so that it assumes a rectangular tubular shape corresponding to the box to be formed. During conveyance of the rectangular tube to a second station, tuckers tuck in, at right angles, a first pair of bottom flaps. At a subsequent station, adhesive is applied to the tucked flaps, and pivotal arms fold a second pair of bottom flaps over and into adhering contact with the fist pair of flaps. The resultant case is thereafter conveyed to a final station where it is presented for filing with the manufacturer's product. An exemplary case packing machine of the foregoing type is the Bemis Series 1547 Case Packer, available from Bemis Packaging Service Machinery Co. of East Minneapolis, Minn.
The above-described KDF methodology is highly efficient, but is only suitable for use in forming containers of rectangular shape. For certain packing applications, a rectangular container may not ideally accommodate (with optimum space efficiency) the item(s) to be packed, e.g., items such as bottles or paper towels having a circular footprint. Also, in situations where the contents of the containers is relatively heavy, a rectangular box may provide insufficient wall strength for stacking. If the product to be packed is a flowable solid such as plastic pellets, the wall panels may lack sufficient stiffness to prevent bulging (elephant footing) of the wall panels.
Non-rectangular containers having oblique wall panels, e.g., octagonal containers, have been developed which are better suited for certain packing applications as described above. However, the known methods for forming such containers lack the simplicity and efficiency of the above-described conveyor line system used to automatically form rectangular containers from KDF precursors. Moreover, for manufacturers desiring to package product in both rectangular and octagonal (or other non-rectangular) containers, it has been necessary to provide separate machines for the set-up and packing of each container type.
Cromwell U.S. Pat. No. 5,624,368 discloses a method and apparatus for erecting an octagonal box structure from a KDF precursor, wherein the precursor is first lowered over a center post. The octagonal container shape takes form as a movably mounted three-sided box folding frame, generally conforming to the angular configuration of three wall panels of the box, advances toward a fixed five-sided box folding frame generally conforming to the desired final configuration of the remaining five wall panels. Wing plates mounted on the post aid in the proper opening of the box. Once the box has been expanded into an octagonal form, a main frame suspended above the box is lowered to provide a progressive folding of end closure flaps.
Bacques et al. U.S. Pat. No. 5,147,271 teaches a method of forming a polygonal, e.g., octagonal, case from an unfolded blank (not a KDF). The method includes wrapping the blank around a mandrel and gluing opposite end panel edges together to form a tubular shape. Thereafter end flaps of the case are folded over and glued.
East et al. U.S. Pat. No. 5,656,006 and Wikstrom U.S. Pat. No. 1,894,209 each disclose formation of a box by advancing, with a mandrel or plunger, an unfolded blank through a forming or folding assembly serving to wrap wall forming panels of the blank about the mandrel or plunger as the blank moves through the folding assembly.
Kondolf U.S. Pat. No. 1,422,580 discloses a box pressing machine comprising a male die which advances into a female die and then expands outwardly to apply final pressure to the sides, ends and corners of a rectangular box carried by the male die into the female die.